1. Field of the Invention
The present invention relates to an apparatus for manufacturing a trapezoidal wire using two-set shaping rollers, and more particularly, to an apparatus for manufacturing a trapezoidal wire using two-set shaping rollers, the apparatus capable of improving an overall reduction rate and reducing a defect rate even at high working speed by using the two-set shaping rollers.
2. Description of the Related Art
A method of manufacturing products using trapezoidal wires includes a method of manufacturing a trapezoidal wire using a separate wire drawing machine and stranding the trapezoidal wire using a stranding machine and a method of manufacturing a trapezoidal wire using a shaping roller in a separate shaping process and stranding the trapezoidal wire using a stranding machine. However, a slow manufacturing speed is a problem for such methods.
U.S. Pat. No. 5,074,140 discloses an apparatus for manufacturing a trapezoidal wire. The apparatus simultaneously shapes and strands a wire using a plurality of shaping roller sets, thereby increasing the manufacturing speed. FIG. 1 illustrates a body 200 of a conventional apparatus for manufacturing a trapezoidal wire, the body 200 having a plurality of shaping roller sets 110, 120, 130, 140, 150, 160, 170, 180 and 190.
Referring to FIG. 1, the shaping roller sets 110, 120, 130, 140, 150, 160, 170, 180 and 190 are disposed along the body 200, and each of the shaping roller sets 110, 120, 130, 140, 150, 160, 170, 180 and 190 includes an upper shaping roller 112 and a lower shaping roller 114. A round wire is inserted between the upper shaping roller 112 and the lower shaping roller 114 of each of the shaping roller sets 110, 120, 130, 140, 150, 160, 170, 180 and 190. Then, each of the shaping roller sets 110, 120, 130, 140, 150, 160, 170, 180 and 190 shapes the round wire into a trapezoidal wire while the body 200 rotates about a rotation axis 201. The trapezoidal wire manufactured by each of the shaping roller sets 110, 120, 130, 140, 150, 160, 170, 180 and 190 is stranded by the rotating body 200.
While the plurality of shaping roller sets 110, 120, 130, 140, 150, 160, 170, 180 and 190 are installed in the body 200 of the conventional apparatus for manufacturing a trapezoidal wire, only one shaping roller set, that is, one-set shaping rollers, is used to shape a wire into a trapezoidal wire. Shaping and stranding a wire using one-set shaping rollers is accompanied by the problem of a wire inserted between the upper and lower shaping rollers 112 and 114 being cut. Such a problem occurs when a shaping speed increases. In other words, when the shaping speed increases, the flow of metal of the wire becomes rapid. In this state, stress working on the wire easily becomes greater than the yield stress of a material of the wire. Consequently, the wire inserted between the upper and lower shaping rollers 112 and 114 is cut.
In addition, the metal flow of the wire between the upper and lower shaping rollers 112 and 114 is not smooth at fast shaping speed. Therefore, a reduction rate, which is a ratio of a cross section of the wire before being shaped to a cross section of the wire after being shaped, is increased. Further, since the wire cannot contact the entire inner surfaces of a shaping portion formed between the upper and lower shaping rollers 112 and 114, a conversion diameter, that is, a value obtained after a cross section of a trapezoidal wire manufactured by the upper and lower shaping rollers 112 and 114 is calculated using a diameter of the round wire, is reduced. Therefore, a wire with a desired cross section cannot be manufactured.
When a wire is inserted between one-set shaping rollers, the wire and the one-set shaping rollers may not be aligned properly. In addition, when the shaping speed of the trapezoidal wire is fast, a side of the inserted wire may be pressed. In this case, a portion of the inserted wire protrudes from the one-set shaping rollers, which is called a lateral flushing phenomenon.